/Engine/Source/Runtime/Engine/Classes/GameFramework/WorldSettings.h
When the bookmark's class is not of the same class as the default bookmark class, the bookmark will be removed on the next update. This will fail if we've overrun MaxNumberOfBookmarks.
The bookmark that was created. Will be nullptr on failure.
[UBookmarkBase](API\Runtime\Engine\Engine\UBookmarkBase) * AddBookmark ( const [TSubclassOf](API\Runtime\CoreUObject\Templates\TSubclassOf)< [UBookmarkBase](API\Runtime\Engine\Engine\UBookmarkBase) > BookmarkClass, const bool bExpandIfNecessary )